Djedatin G.,AfricaRice |
Djedatin G.,University Abomey Calavi |
Ndjiondjop M.-N.,AfricaRice |
Mathieu T.,CNRS Plant Genome and Development Laboratory |
And 6 more authors.
Plant Disease | Year: 2011
Xanthomonas oryzae pv. oryzae is the causal agent of bacterial blight in rice, one of the most devastating diseases of rice worldwide. African X. oryzae pv. oryzae strains belong to a clear genetic group distinct from those of Asia. Three new races of the pathogen were characterized among strains from West Africa. We evaluated 107 Oryza glaberrima accessions for resistance to bacterial blight under greenhouse conditions. Six-week-old seedlings were inoculated with five different African X. oryzae pv. oryzae strains originating from the West African nations of Burkina and Mali and representing different races (A1, A2, and A3). Philippine X. oryzae pv. oryzae strain PXO86 (race 2) was also used. Most (48%) of the accessions of O. glaberrima were highly susceptible to X. oryzae pv. oryzae strains from Burkina, while 20 and 36 were resistant to X. oryzae pv. oryzae strains from Mali and the Philippines, respectively. CAPS markers and dot blot assays were used for detection of resistance genes xa5 and Xa21 from a selected set of O. glaberrima accessions. Our results suggest that the O. glaberrima germplasm contains a narrow genetic base for resistance to X. oryzae pv. oryzae. Sources of resistance identified among O. glaberrima are recommended for rice breeding programs to develop bacterial blightresistant cultivars for West Africa. © 2011 The American Phytopathological Society.
Diwani T.N.,German Development Service DED |
Asch F.,University of Hohenheim |
Becker M.,University of Bonn |
Journal of Plant Nutrition and Soil Science | Year: 2013
Kakamega district in Western Kenya represents the smallholder farming systems typical for much of the densely populated humid highlands in East Africa. A specific feature, however, is the presence of a protected forest reserve (Kakamega Forest National Park), covering some 20% of the district area. Year-round crop production with little use of external inputs is resulting in declining soil fertility and crop yields. Technologies to counteract fertility constraints are rarely implemented, as they do not consider system diversity or farm-specific characteristics. We surmised that farm type-specific targeting of technology options to address soil fertility-related production constraints would reduce the anthropogenic pressure on the resources of the adjacent Kakamega rainforest reserve. Based on Kenyan national census data, we selected 168 farms in physical proximity of the Kakamega forest and characterized them regarding production system and soil attributes. Cluster and principal component analyses identified five distinct farm categories. Three representative farms from each cluster group were subsequently selected to establish labor-use patterns, draw resource-flow maps, and determine NPK balances. Small subsistence-oriented farms were most common (> 50%), with maize yields of 0.9 t ha-1 (Cluster 1). Most farmers relied on the forest to provide fire wood, animal feed, and medicinal plants. Mixed farms, combining subsistence maize with industrial crops, were differentiated by soil type, with tea being grown on Ferralsol (Cluster 3), and sugar cane being grown on Acrisol (cluster 4). The dependence on forest resources was limited to animal grazing and the collection of feed stuff (Cluster 3), or the extraction of medicinal plants (Cluster 4). Only few farms showed a high degree of market orientation of the food-crop production. These comprised either small farms with high investments in fertilizer and maize yields close to 2 t ha-1 (Cluster 2), or larger farms (1.6-3.9 ha) with low fertilizer but high hired-labor use (Cluster 5). Their reliance on forest resources was generally low. Resource flows showed mainly patterns of nutrient export in subsistence farms, and more complex flow patterns, involving several farm compartments, in the diversified farms. Partial nutrient balances were strongly negative for N and K, irrespective of soil or farm type. Soil-fertility characteristics reflected the nutrient balances with generally low C and N in all farms on Acrisol, and low P in farms not applying mineral fertilizers or farmyard manure. The proposed typology is expected to improve the targeting of technologies addressing soil fertility-related production constraints, and to reduce the pressure on forest resources. This is of particular importance in the case of small-scale subsistence and mixed farms close to the forest margin. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Rodenburg J.,Africa Rice Center |
Demont M.,International Rice Research Institute |
Sow A.,AfricaRice |
Crop Protection | Year: 2014
Weeds and grain feeding birds are the two main biological causes of yield losses in irrigated rice in Africa. To quantify the single and combined effect of these biological constraints on rice yields, and to investigate whether weeds attract birds and thereby contribute to increased bird damage, a three-year factorial experiment was set-up in the Senegal River Valley. We tested two management factors (bird and weed management), each with two levels ('complete' and 'absent'), and one crop cycle factor also with two levels (Sahel 202, a medium-cycle and Sahel 108, a short-cycle rice cultivar). Season-long competition from weeds resulted in high but predictable yield losses ranging from 50% to 75%, with lower yield losses for the medium-cycle cultivar Sahel 202 in two of the three seasons. Due to the nature of the pest, season-long exposure to birds resulted in less predictable yield losses ranging from 13% to as high as 94%, with high seasonal variation. In two seasons, much lower bird-inflicted yield losses were observed in the short-cycle cultivar Sahel 108, whereas in one season the medium-cycle cultivar Sahel 202 was much less damaged. When rice was exposed to both weeds and birds, the relative yield losses ranged from 80 to 99%. The yield reducing effect of weeds and birds was never additive. Bird visits to a weedy crop were more frequent compared to a weed-free crop at least in the early rice grain filling stages. This attraction of birds by weeds resulted in an additional yield loss in five of the six cases, ranging from 2 to 62%. Bird-inflicted yield losses in irrigated rice may be reduced by keeping the crop, as much as possible, free from weeds. © 2014 Elsevier Ltd.
Yamano T.,International Rice Research Institute |
Arouna A.,AfricaRice |
Labarta R.A.,International Center for Tropical Agriculture |
Huelgas Z.M.,International Rice Research Institute |
Mohanty S.,International Rice Research Institute
Global Food Security | Year: 2016
To meet rising demand for rice, it is estimated that the global rice production needs to increase by 116 million tons by 2035. Much of the increase has to come from smallholder rice farmers in developing countries. In this article, we review 25 evaluation studies on new rice technologies and practices that have been tried and used by smallholder rice farmers in developing countries. Stress-tolerant rice varieties are found among promising new rice varieties. African farmers benefit from New Rice for Africa (NERICA) varieties. Some natural resource management (NRM) practices have been evaluated in farmer trials and found beneficial. However, the NRM evaluation studies faced with difficulties in defining NRM "technology" and "adoption", and the difficulties remain as future challenges for evaluation studies. © 2016.
PubMed | University of Alberta, Duke University, AfricaRice, National Taiwan University and Biosciences eastern and central Africa BecA
Type: Journal Article | Journal: PloS one | Year: 2016
African rice gall midge (AfRGM) is one of the most destructive pests of irrigated and lowland African ecologies. This study aimed to identify the quantitative trait loci (QTL) associated with AfRGM pest incidence and resistance in three independent bi-parental rice populations (ITA306xBW348-1, ITA306xTOG7106 and ITA306xTOS14519), and to conduct meta QTL (mQTL) analysis to explore whether any genomic regions are conserved across different genetic backgrounds. Composite interval mapping (CIM) conducted on the three populations independently uncovered a total of 28 QTLs associated with pest incidence (12) and pest severity (16). The number of QTLs per population associated with AfRGM resistance varied from three in the ITA306xBW348-1 population to eight in the ITA306xTOG7106 population. Each QTL individually explained 1.3 to 34.1% of the phenotypic variance. The major genomic region for AfRGM resistance had a LOD score and R2 of 60.0 and 34.1% respectively, and mapped at 111 cM on chromosome 4 (qAfrGM4) in the ITA306xTOS14519 population. The meta-analysis reduced the number of QTLs from 28 to 17 mQTLs, each explaining 1.3 to 24.5% of phenotypic variance, and narrowed the confidence intervals by 2.2 cM. There was only one minor effect mQTL on chromosome 1 that was common in the TOS14519 and TOG7106 genetic backgrounds; all other mQTLs were background specific. We are currently fine-mapping and validating the major effect genomic region on chromosome 4 (qAfRGM4). This is the first report in mapping the genomic regions associated with the AfRGM resistance, and will be highly useful for rice breeders.
Sumberg J.,University of Sussex |
Raboanarielina C.,AfricaRice |
Outlook on Agriculture | Year: 2013
Agricultural research for development (AR4D) is often discussed in terms of abandoning 'business as usual'. One important element of the reframing of agricultural research is an emphasis on the development of useful 'products', which immediately brings 'users' to centre stage. In this paper the authors review the literature on user involvement from the field of new product development (NPD). They then propose a conceptual model of feedback and feedback loops within AR4D and use this model to analyse examples of feedback generation in rice research in West Africa. On the basis of this initial analysis they conclude that, while there are many ongoing activities that could potentially provide useful feedback, in the majority of cases this potential is probably not being realized. Unless feedback is approached much more systematically, the promise of AR4D as a means of generating useful products for farmers and others will probably remain unfulfilled.
Ochola D.,National Crops Resources Institute NaCRRI |
Issaka S.,AfricaRice |
Rakotomalala M.,British Petroleum |
Pinel-Galzi A.,Montpellier University |
And 7 more authors.
Virus Research | Year: 2015
Epidemics of rice yellow mottle virus (RYMV) have developed recently in eastern Uganda, close to Lake Victoria in East Africa. Unexpectedly, all isolates from the affected area belonged to a single strain (named S4ug), a strain that is different from the S4lv strain that has been prevalent in the Lake Victoria basin for the past five decades. Interestingly, the S4ug strain is most closely related at the genomic level (except ORF1) to the strain present in Madagascar (S4mg), 2000. km away. The minor parent of the S4mg recombinant strain could not be detected. Molecular clock dating analysis indicated that the singular sequence of events - that associated the emergence of a new strain (S4ug), a modular recombination between closely related strains (S4mg and S4ug) and a long distance transmission (S4mg) - occurred recently, within the past few decades. This finding is at variance with the process of gradual strain dispersal and diversification over two centuries throughout Africa that was previously established. © 2014 Elsevier B.V.
De Rouw A.,University Pierre and Marie Curie |
Casagrande M.,University of Lyon |
Phaynaxay K.,National University of Laos |
Soulileuth B.,Managing Soil Erosion Consortium |
Weed Research | Year: 2014
Summary: Crops in shifting cultivation fields often suffer from severe weed infestation when long fallow periods are replaced by short fallow periods. The soil seedbank as a source of weed infestation was studied in four fields that differed in their last fallow duration. The effect of burning was analysed by comparing adjacent pre-burn and post-burn samples (two sites). Surface vegetation was monitored from burning to harvest in the plots from which soil samples were taken to determine the fraction of the seedbank germinating (three sites). Seedbank size (1700-4000 seedlings m-2) varied depending on a single species, Mimosa diplotricha. Burning reduced emergence of most species, but stimulated emergence in others. Densities in the seedbank were not correlated with above-ground abundances in the field, except for some species. Most species emerging after 50 days from the soil samples (40% of seedlings) were absent from the field after 190 days. Whilst the data from this study are derived from only four fields, the weed problems after short-term fallowing appeared to be due to a larger fraction of the seedbank emerging, possibly due to shallow burial, and to a floristic shift towards adaption to burning, rather than the size of the seedbank per se. © 2013 European Weed Research Society.
PubMed | University of Dar es Salaam, AfricaRice, Montpellier University, British Petroleum and 3 more.
Type: | Journal: Virus research | Year: 2014
Epidemics of rice yellow mottle virus (RYMV) have developed recently in eastern Uganda, close to Lake Victoria in East Africa. Unexpectedly, all isolates from the affected area belonged to a single strain (named S4ug), a strain that is different from the S4lv strain that has been prevalent in the Lake Victoria basin for the past five decades. Interestingly, the S4ug strain is most closely related at the genomic level (except ORF1) to the strain present in Madagascar (S4mg), 2000km away. The minor parent of the S4mg recombinant strain could not be detected. Molecular clock dating analysis indicated that the singular sequence of events - that associated the emergence of a new strain (S4ug), a modular recombination between closely related strains (S4mg and S4ug) and a long distance transmission (S4mg) - occurred recently, within the past few decades. This finding is at variance with the process of gradual strain dispersal and diversification over two centuries throughout Africa that was previously established.
Zossou E.,University of Liège |
van Mele P.,AfricaRice |
Vodouhe S.D.,University Abomey Calavi |
International Journal of Agricultural Sustainability | Year: 2010
When the Africa Rice Center (AfricaRice)1 introduced improved parboiling technology in Benin in 2006 through farmerto-farmer video, it enhanced women's creativity and motivation to parboil more and better the quality of rice. Their rice attracted more buyers and fetched a higher price which increased their profits and strengthened the women's social cohesion. The video motivated women to start parboiling as a group and to express group-based requests for credit and training. However, newly established women's groups in villages with strong negative experiences from the cotton sector did not last because of fear and mistrust. The video helped local non-governmental organizations (NGOs) to improve their training methods and strengthened their relations with rural communities and between the women rice processors and input and output markets. Although these NGOs responded by facilitating access to micro-finance institutions, they were unwilling to provide credit to the groups because of past bad experiences. Instead, informal credit suppliers proved more responsive. Rice producers who attended the open-air video shows at the same time as the women rice processors became more willing to sell them rice on credit. We discuss the conditions and challenges of farmer-to-farmer video in creating organizational and institutional changes among service providers and rural entrepreneurs. © 2010 Earthscan.